Mar-resistant oligomeric-based coatings

ABSTRACT

A curable coating composition comprising functionalized oligomer components i and ii which cross-link at cure to form a three-dimensional network having chains of substantially uniform, controllable molecular weight between cross-links; oligomers i and ii having weight average molecular weights not exceeding about 3,000, a polydispersity for (i) not exceeding about 1.5, and functionalities that react with one another to cross-link i and ii at cure to yield coatings with an excellent balance of hardness and mar resistance.

This application is a divisional of application of Ser. No. 09/180,509filed on Nov. 12, 1998 allowed on Oct. 22, 2001 as U.S. Pat. No.6,376,596, which is a 371 of PCT/US97/08179 filed on May 14, 1997.

BACKGROUND OF THE INVENTION

The present invention relates to a curable coating compositionparticularly useful as a topcoat in multi-layered coating systems.

Basecoat-clearcoat systems have found wide acceptance in the past decadeas automotive finishes. Continuing effort has been directed to suchcoating systems to improve the overall appearance, the clarity of thetopcoat, and the resistance to deterioration. Further effort has beendirected to the development of coating compositions having low volatileorganic content (VOC). A continuing need exists for coating formulationswhich provide outstanding performance characteristics after application,and particularly mar-resistance and resistance to environmental etching.Heretofore, mar-resistant coatings were attained by softening thecoating, which depreciates other performance characteristics. Theinstant invention overcomes this problem.

SUMMARY OF THE INVENTION

This invention concerns a curable coating composition of a binder in anorganic solvent, the composition having a volatile organic content notexceeding about 0.4 kilograms per liter, comprising:

i) a binder selected from a linear or branched cycloaliphaticmoiety-containing oligomer or blend of oligomers with a weight averagemolecular weight not exceeding about 3,000, a polydispersity notexceeding about 1.5 and functionality A or A plus B; and

ii) an optional oligomeric crosslinker or blend of crosslinkers with aweight average molecular weight not exceeding about 3,000 andfunctionality C or C plus D;

components i and ii reacting at cure to form a three-dimensional networkhaving chains of substantially uniform, controllable molecular weightbetween crosslinks.

Preferred functionalities in oligomeric components i and ii are asfollows:

COMPONENT (i) COMPONENT (ii) A = hydroxyl C = isocyanate A = hydroxyl C= melamine A = anhydride C = epoxy A = anhydride C = epoxy; D = hydroxylA = acid C = epoxy A = acid; B = hydroxyl C = epoxy; D = melamine A =epoxy C = isocyanate A = epoxy; B = hydroxyl C = isocyanate A = aldimineC = isocyanate A = aldimine; B = hydroxyl C = isocyanate A = ketimine C= isocyanate A = ketimine; B = hydroxyl C = isocyanate A = silane C =silane A = silane; B = hydroxyl C = melamine A = silane; B = hydroxyl C= isocyanate A = silane; B = epoxy C = acid; D = melamine

The compositions of this invention, comprising (i) when (i) isself-crosslinking, or, (i) plus (ii), may also contain up to a total ofabout 30% based on the total binder of a noncyclic oligomer and/or anacrylic polymer and/or a dispersed macromolecular polymer as describedin more detail hereafter. This invention also concerns a method forcoating a substrate comprising applying the disclosed compositionthereto and curing the composition, as well as a substrate coated withthe composition. The term “isocyanate(s)” employed herein includesblocked isocyanate(s) as well.

DETAILS OF THE INVENTION

The compositions of this invention form structured polymer networks ofhigh hardness and excellent mar resistance. The functionality of theseoligomers is predictably (nonrandomly) located versus polymers in whichfunctionality is randomly distributed and whose polydispersitiesgenerally exceed 2.0. By “polydispersity” is meant weight averagemolecular weight divided by number average molecular weight, bothmeasured by gel permeation chromatography. In compositions of thisinvention, molecular weight between crosslinks can be controlled to formmore uniform networks minimizing short, embrittling lengths and long,softening lengths; minimizing soluble non-functional materials in thenetwork and maximizing the toughness of the films (energy to break).These systems develop open networks with high molecular weight betweencrosslinks, vs. polymeric systems, at relatively high Tg's.

The Tg of these systems can be controlled to give a maximum balance ofmar, hardness, durability, and etch. In measuring Tg of crosslinkedfilms made from compositions of this invention using dynamic mechanicalanalysis, the Tg regime is characterized by a steep slope versus agradual slope for a random system based on polymers. The reactivity ofthese systems is such that complete reaction is attainable to minimizehydrophilic groups. These systems are typically baked at 120° to 141° C.(250° to 285° F.), but can be cured at lower temperatures through theuse of more reactive groups and catalysis.

Representative of the functionalized oligomers that can be employed ascomponent i or ii are the following:

Acid Oligomers: The reaction product of multifunctional alcohols such aspentaerythritol, hexanediol, trimethylol propane, and the like, withcyclic monomeric anhydrides such as hexahydrophthalic anhydride,methylhexahydrophthalic anhydride, and the like.

Hydroxyl Oligomers: The above acid oligomers further reacted withmonofunctional epoxies such as butylene oxide, propylene oxide, and thelike.

Anhydride Oligomers: The above acid oligomers further reacted withketene.

Silane Oligomers: The above hydroxyl oligomers further reacted withisocyanato propyl trimethoxy silane.

Epoxy Oligomers: The diglycidyl ester of cyclohexane dicarboxylic acid,such as AralditeÒ CY—184 from Ciba Geigy, and cycloaliphatic epoxies,such as ERLÒ—4221, and the like from Union Carbide.

Isocyanate Oligomers: The isocyanurate trimer of hexamethylenediisocyanate, DESMODURÒ 3300 from Bayer or Tolonate HDTâ fromRhone-Poulenc, and the isocyanurate trimer of isophorone diisocyanate,and the like.

Aldimine Oligomers: The reaction product of isobutyraldehyde withdiamines such as isophorone diamine, and the like.

Ketimine Oligomers: The reaction product of methyl isobutyl ketone withdiamines such as isophorone diamine.

Melamine Oligomers: Commercially available melamines such as CYMELÒ 1168from Cytec Industries, and the like.

AB-Funtionalized Oligomers: Acid/hydroxyl functional oligomers made byfurther reacting the above acid oligomers with 50%, based onequivalents, of monofunctional epoxy such as butylene oxide or blends ofthe hydroxyl and acid oligomers mentioned above or any other blenddepicted above.

CD-Functionalized Crosslinkers: Epoxy/hydroxyl functional crosslinkerssuch as the polyglycidyl ether of Sorbitol DCE—358Ò from Dixie Chemicalor blends of the hydroxyl oligomers and epoxy crosslinkers mentionedabove or any other blend as depicted above.

The compositions of this invention may additionally contain up to 30% byweight of binder of a noncyclic oligomer, i.e., one that is linear oraromatic. Such noncyclic oligomers can include, for instance, succinicanhydride- or phthalic anhydride-derived moieites in the “AcidOligomers” such as described above.

Preferred oligomers (i) have weight average molecular weight notexceeding about 3,000 with a polydispersity not exceeding about 1.5;more preferred oligomers have molecular weight not exceeding about 2,500and polydispersity not exceeding about 1.4; most preferred oligomershave molecular weight not exceeding about 2,200, and polydisperity notexceeding about 1.25. The compositions of this invention can comprise100% by weight of component (i) when (i) is a self-crosslinker. Moretypically, compositions will comprise 20-80 weight percent of (i),preferably 30 to 70 weight percent and more preferably 40 to 60 weightpercent, with the balance being (ii).

The present coating composition can further comprise a functional amountof catalyst, generally about 0.1 to 5 weight percent, based on theweight of solids in the formulation. A wide variety of catalysts can beused, such as dibutyl tin dilaurate for isocyanate based reactions,tertiary amines such as triethylenediamine or phosphonium basedcatalysts for epoxy reaction and sulfonic acids, such as dodecylbenzenesulfonic acid for melamine reactions.

The coating compositions of the present invention are formulated intohigh solids coating systems dissolved in at least one solvent. Thesolvent is usually organic. Preferred solvents include aromatichydrocarbons such as petroleum naphtha or xylenes; ketones such asmethyl amyl ketone, methyl isobutyl ketone, methyl ethyl ketone oracetone; esters such as butyl acetate or hexyl acetate; and glycol etheresters such as propylene glycol monomethyl ether acetate.

The coating compositions of the present invention can also contain up to30% of total binder of an acrylic polymer of weight average molecularweight greater than 3,000, or a conventional polyester such as SCDÒ—1040from Etna Product Inc. for improved appearance, sag resistance, flow andleveling and such. The acrylic polymer can be composed of typicalmonomers such as acrylates, methacrylates, styrene and the like andfunctional monomers such as hydroxy ethyl acrylate, glycidylmethacrylate, or gamma methacrylyl propyl trimethoxy silane and thelike.

The coating compositions of the present invention can also contain up to30% of total binder of a dispersed acrylic component which is a polymerparticle dispersed in an organic media, which particle is stabilized bywhat is known as steric stabilization. Hereafter, the dispersed phase orparticle, sheathed by a steric barrier, will be referred to as the“macromolecular polymer” or “core”. The stabilizer forming the stericbarrier, attached to this core, will be referred to as the “macromonomerchains” or “arms”.

The dispersed polymer contains about 10 to 90%, preferably 50 to 80%, byweight, based on the weight of the dispersed polymer, of a highmolecular weight core having a weight average molecular weight of about50,000 to 500,000. The preferred average particle size is 0.1 to 0.5microns. The arms, attached to the core, make up about 10 to 90%,preferably 10 to 59%, by weight of the dispersed polymer, and have aweight average molecular weight of about 1,000 to 30,000, preferably1,000 to 10,000.

The macromolecular core of the dispersed polymer is comprised ofpolymerized acrylic monomer(s) optionally copolymerized withethylenically unsaturated monomer(s). Suitable monomers include styrene,alkyl acrylate or methlacrylate, ethylenically unsaturatedmonocarboxylic acid, and/or silane-containing monomers. Such monomers asmethyl methacrylate contribute to a high Tg (glass transitiontemperature) dispersed polymer, whereas such “softening” monomers asbutyl acrylate or 2-ethylhexylacrylate contribute to a low Tg dispersedpolymer. Other optional monomers are hydroxyalkyl acrylates ormethacrylates or acrylonitrile. Optionally, the macromolecular core canbe crosslinked through the use of diacrylates or dimethacrylates such asallyl methacrylate or post reaction of hydroxyl moieties withpolyfunctional isocyanates.

The macromonomer arms attached to the core can contain polymerizedmonomers of alkyl methacrylate, alkyl acrylate, each having 1 to 12carbon atoms in the alkyl group, as well as glycidyl acrylate orglycidyl methacrylate or ethylenically unsaturated monocarboxylic acidfor anchoring and/or crosslinking. Typically useful hydroxy-containingmonomers are hydroxy alkyl acrylates or methacrylates as describedabove.

The coating compositions of the present invention can also containconventional additives such as pigments, stabilizers, rheology controlagents, flow agents, toughening agents and fillers. Such additionaladditives will, of course, depend on the intended use of the coatingcomposition. Fillers, pigments, and other additives that would adverselyeffect the clarity of the cured coating will not be included if thecomposition is intended as a clear coating.

The coating compositions are typically applied to a substrate byconventional techniques such as spraying, electrostatic spraying, rollercoating, dipping or brushing. The present formulations are particularlyuseful as a clear coating for outdoor articles, such as automobile andother vehicle body parts. The substrate is generally prepared with aprimer and or a color coat or other surface preparation prior to coatingwith the present compositions.

After application to a substrate, the present compositions can be curedby heating to a temperature of about 120°-150° C. for a period of about15 to 90 minutes.

The present invention is further illustrated by the following Proceduresand Examples, in which parts and percentages are by weight unlessotherwise indicated. VOC determinations are made by the procedure ofASTM method D3960.

Procedure 1 TETRA HYDROXYL FUNCTIONAL OLIGOMER

Preparation of Acid Oligomer

To a 12-liter flask fitted with an agitator, condenser, heating mantle,nitrogen inlet, thermocouple and an addition port was added 2447.2 gmsof propylene glycol monomethylether acetate, 792.4 gms ofpentaerythritol and 1.36 gms of triethylamine. The reaction mixture wasagitated and heated to 140° C. under a nitrogen blanket at which time3759 gms of methyl hexahydrophthalic anhydride was added over 6 hrs. Thereaction mixture was then held at 140° C. until no anhydride bands wereobserved on an infrared spectroscopic trace.

Preparation of Diol

To a 5-liter flask fitted with an agitator, condenser, heating mantle,nitrogen inlet, thermocouple and an addition port was added 2798.4 gmsof acid oligomer prepared above and 2.76 gms of triethylamine. Themixture was agitated and heated to 60° C. under nitrogen. Then, 696.9gms of 1,2-epoxy butane was added over 120 mins, after which thetemperature was raised to 105° C. and held at that temperature until theacid number dropped to about 10 or less. Percent weight solids were71.5, Gardner viscosity V, number average molecular weight 895 andweight average molecular weight 1022 as determined by GPC (polystyrenestandard).

Procedure 2 DI HYDROXYL FUNCTIONAL OLIGOMER

Preparation of Acid Oligomer

To a 12-liter flask fitted with an agitator, condenser, heating mantle,nitrogen inlet, thermocouple and an addition port was added 2434.5 gmsof propylene glycol monomethylether acetate, 1222.5 gms of hexane dioland 1.37 gms of triethylamine. The reaction mixture was agitated andheated to 140° C. under a nitrogen blanket at which time 3341.6 gms ofmethyl hexahydrophthalic anhydride was added over 6 hrs. The reactionmixture was then held at 140° C. until no anhydride bands were observedon an infrared spectroscopic trace.

Preparation of Oligomeric Diol

To a 5-liter flask fitted with an agitator, condenser, heating mantle,nitrogen inlet, thermocouple and an addition port was added 2020.4 gmsof acid oligomer prepared above and 2.45 gms of triethylamine. Themixture was agitated and heated to 60° C. under nitrogen. Then, 478.3gms of 1,2-epoxy butane was added over 120 mins, after which thetemperature was raised to 105° C. and held at that temperature until theacid number dropped to about 10 or less. Percent weight solids were69.5, Gardner viscosity A, number average molecular weight 679 andweight average molecular weight 770 as determined by GPC (polystyrenestandard).

Procedure 3 HYDROXYL/SILANE OLIGOMER

The oligomer from Procedure 2 was further reacted by mixing

di hydroxyl functional oligomer 250 isocyanato propyl trimethoxy silane60.9 1% dibutyl tin dilaurate in methylethyl 0.25 ketone (MEK)

The above mixture was heated at 60° C. for 3 days. The completion of thereaction was monitored by infra red spectroscopy. The reaction wascomplete when there was essentially no isocyanate absorption in the IR.

Procedure 4 ANHYDRIDE OLIGOMER

The anhydride oligomer was prepared from a tetra-functional half-acidester. The following constituents were charged to a reaction vesselequipped with a heating mantle, reflux condenser, thermometer, nitrogeninlet, and stirrer:

Parts by Weight Portion I pentaerythritol 478.0 methyl hexahydrophthalicanhydride 2250.0 triethylamine 0.5 Portion II xylol (135°-145° C.)2250.0 Total 4978.5

Portion 1 was charged into the reaction vessel, heated to 180° C. undera nitrogen blanket and held for 30 minutes. After the hold period, thereaction mixture was cooled and Portion 2 added.

The solution prepared above was used to make a linear pendant anhydride.The solution was charged into a 5L flask equipped with a stirrer and agas inlet tube. The gas inlet tube was attached to a ketene generatorsimilar to the one described by Williams et al in the Journal of OrganicChemistry 5, 122, 1940. Ketene was bubbled through the solution untilall of the acid groups were converted to anhydride groups. Solvent wasthen removed under vacuum to give a linear pendant anhydride with thefollowing characteristics:

percent weight solids: 78.0 anhydride eq. wt.:  329 ± 4 (on solutionbasis) acid eq. wt.: 6176 ± 1323 (on solution basis) weight average molwt. = 1100.

EXAMPLE 1

ISOCYANATE CLEAR Parts by Weight Part I tetra hydroxyl functionaloligomer 217.71 (Procedure 1) di hydroxyl functional oligomer 149.24(Procedure 2) propylene glycol mono methyl ether acetate 26.14 (PMacetate) TinuvinÒ 384 (UV screener from Ciba Geigy) 8.94 TinuvinÒ 292(hindered amine light stabilizer 6.72 from Ciba Geigy) 10% BYK-301Ò(flow additive from BYK Chemie) 1.78 in PM acetate 10% di butyl indilaurate in methyl ethyl ketone 1.12 butyl acetate 52.27 Part IITolonateÒ HDT (isocyanurate trimer of 192.23 hexamethylene diisocyanatefrom Rhone-Poulenc)

This coating was sprayed over a black waterborne basecoat which hadalready received a warm air flash of 5 min at 82° C. (180° F.). Thecoating was cured for 30 min at 141° C. (285° F.). The coating exhibitedexcellent appearance, hardness and mar resistance. This coatingexhibited higher hardness and significantly better mar resistance than astandard coating made at a similar final film Tg using a routinehydroxyl functional acrylic polymer (6,000 weight average molecularweight polymer with 32% hydroxy ethyl acrylate). The acrylic resin wassubstituted for the oligomer on an equivalent basis.

POLYMERIC 2K PROPERTY OLIGOMERIC 2K CLEAR CLEAR Glass Transition 42.7°C. 48.1° C. Temperature¹ Hardness² 141 N/mm² 130 N/mm² Wet mar³ 80%50.6% Dry mar⁴ 94.2% 65.5% ¹as measured by differential scanningcalorimetry ²as measured using a FisherscopeÒ hardness tester (themeasurement is in Newtons per square millimeter) ³the surface of a panelis marred using a 3% slurry of aluminum oxide in water and a felt pad,the marring is accomplished using a DaieiÒ Rub Tester. The test uses 10cycles with a weight of 500 grams. The rating shown is the percent ofthe surface which is not marred as measured by image analysis. ⁴thesurface of a panel is marred using Bon AmiÒ Cleanser and a felt pad, themarring is accomplished using a DaieiÒ Rub Tester. The test uses 15cycles with a weight of 700 grams. The rating shown is the percent ofthe surface which is not marred as measured by image analysis.

EXAMPLE 2

ANHYDRIDE/EPOXY CLEAR Parts by Weight Part I anhydride oligomer(Procedure 4) 763.08 TinuvinÒ 384 (UV screener from Ciba Geigy) 19.08TinuvinÒ 292 (hindered amine light syabilier 13.74 from Ciba Geigy) 5%BYK-301Ò (flow additive from BYK Chemie) 56.4 in PM acetate 25% tetrabutyl phosphonium chloride 19.84 in PM acetate butyl acetate 97.0 PartII diglycidyl ester of cyclohexane dicarboxylic acid 358.65

This coating was sprayed over a black waterborne basecoat which hadalready received a warm air flash of 5 min at 82° C. The coating wascured for 30 min at 141° C. This coating exhibited excellent appearance,hardness, cure and durability. This coating exhibited significantlybetter durability than a similar coating based on a standard acrylicanhydride polymer (a 6,000 weight average molecular weight polymercontaining 27% itaconic anhydride). The acrylic was substituted for theoligomer on an equivalent basis. On accelerated QUV testing (using anFS-40 bulb), the polymeric anhydride based coating cracked after4,000-6,000 hours of exposure; the oligomeric based coating showed nocracking and had excellent gloss at over 10,000 hours of exposure.

EXAMPLE 3

MELAMINE CLEAR Parts by Weight Part I tetra hydroxyl functional oligomer16.1 (Procedure 1) di hydroxyl functional oligomer 16.6 (Procedure 2)CymelÒ 1168 (melamine from Cytec Ind.) 16.1 20% BYK-301Ò (flow additivefrom BYK Chemie) 0.4 in PM acetate catalyst solution* 0.8 *catalystsolution CycatÒ 600 (sulfonic acid from American 48.0 Cyanamid) AMP-95Ò(amine from Angus Chemical) 10.8 methanol 41.2

This coating was applied over a black waterborne basecoat which hadalready received a warm air flash of 5 min at 82° C. The coating wascured for 30 min at 141° C. This coating exhibited good appearance,hardness, and mar resistance.

EXAMPLE 4

SILANE (a)/HYDROXYL (b)/ISOCYANATE (c) Parts by Weight Part I tetrahydroxyl functional oligomer 243.5 (Procedure 1) hydroxyl/silaneoligomer 175.9 (Procedure 3) TinuvinÒ 384 (UV screener from Ciba Geigy)9.47 TinuvinÒ 292 (hindered amine light stabilier 6.97 from Ciba Geigy)10% BYK-301Ò (flow additive from BYK Chemie) 3.29 in PM acetate 10% dibutyl tin dilaurate in butyl acetate 1.04 butyl acetate 26.3 PM acetate26.3 Part II TolonateÒ HDT (isocyanurate trimer of 157.2 hexamethylenediisocyanate from Rhone-Poulenc)

This coating was sprayed over a black waterborne basecoat which hadalready received a warm air flash of 5 min at 82° C. The coatingexhibited excellent appearance, hardness and mar resistance.

EXAMPLE 5

A.) Nonaqueous Dispersion

To a 5-liter flask fitted with a agitator, thermometer, condenser andaddition funnels was added the following ingredients. The mixture wasagitated under nitrogen and temperature raised to reflux (100° to 104°C.). Ingredients are given in parts by weight (to the nearest wholenumber, for most). The dispersed polymer is 63.5% weight solids intoluene having a weight average molecular weight of 8100. Thecomposition was as follows:

STY/BA/BMA/HEA/MAA/GMA (14.7/43.6/27.5/10.1/2.3/1.7) dispersed polymer206 isopropanol 12 spirits 94 heptane 53 butanol 3

Added as a shot at reflux was t-butyl peroctoate (0.5 parts) and mineralspirits (5 parts). Then, the following ingredients were added over a 210minute period at reflux:

styrene 52 hydroxy ethylacrylate 86 methyl methacrylate 126 glycidylmethacrylate 5 methacrylic acid 14 methyl acetate 62 dispersed polymer103

These ingredients were added next and the reaction held for 45 minutes:

butanol 12 heptane 17 t-butyl peroctoate 5 mineral spirits 31

Butanol (16 parts) and t-butyl peroctoate (1.7 parts) were then addedover a 30 minute period and the reaction was held for 60 minutes.Finally, the reactor was stripped of 76 parts of solvent. The particlesize was 298 nm as measured by quasielastic light scattering and had aroom temperature viscosity of 2000 centipoise at 5 rpm on a Brookfieldviscometer and a weight solids of 63.5 percent.

B.) Acrylosilane Resin

The resin was made by this procedure: charge 400 g of 2 ethyl hexanoland 400 g of N-pentyl propionate to a 5 liter flask. Heat to reflux.Premix and add 896 g of styrene, 672 g of gamma methacryl propyltrimethoxy silane, 336 g of 2-ethyl hexyl methacrylate, 336 g ofhydroxypropyl methacrylate, 170.2 g of 2.2(2 methyl butane nitrile), 40g of 2 ethyl hexanol, and 40 g of N-pentyl propionate to the refluxingmaterial over a period of six hours. After the addition, hold thetemperature for 30 minutes. Then, add a premixed blend of 40 g of 2ethyl hexanol, 40 g of N-pentyl propionate and 9 g of 2.2(2 methylbutane nitrile) over a 30 minute period. Hold the temperature for 30minutes after addition, then cool and empty.

Gardner Holt Viscosity Weight Solids Weight Ave. M.W. X + 1/2 73.3% 5686

C.) Cyclosilane Oligomer (i)

Place some cyclohexanedimethanol in the oven to melt. Once melted, take294.7 g of cyclohexanedimethanol along with 0.11 g FascatÒ 420 (tincatalyst from Elf Atochem) and place in a flask at about 35° C. Then,add 839 g of isocyanate propyl trimethoxysilane over 75 minutes. Thenhold for two hours. Cool and empty.

Gardner Holt Viscosity Weight Solids Weight Ave. M.W. V 90% 1550

D.) Silanated Star Polyester (i)

Ingredient Weight Step I: Add the following ingredients to the reactor,heat to 120° C.- 125° C. Allow batch to exotherm to 145° C. If exothermdoes not happen heat to 145° C. Hold for 1 hour at 145° C. beforeproceeding. pentaerythritol 280.2 4-methyl hexahydrophthalic anhydride1037.8 butyl acetate 161.1 Step II: Feed the ingredients over 30 minutesat 145° C. Maintain the 145° C. temperature. Cardura E (monoepoxy fromShell Chemical) 1561.9 butyl acetate 182.3 Step III: Add as a shot toreactor. Heat to 175° C. Record Acid Number vs. time profile, every 30minutes after reaching 175° C., until it stabilizes. dibutylin dilaurate2.9 butyl acetate 71.7 Step IV: Once acid number has stabilized, cool tobelow 100° C. Dilute with butyl acetate. butyl acetate 302 Batch Total3600 wt. solids = 80% Acid Number < 2.

In a reaction flask, place 3720 g of the star polyester made immediatelyabove, 1524 g of isocyanate propyl trimethoxysilane and 0.1 g Fascat 420catalyst. Stir for 90 minutes. Blanket the whole time with N₂.

wt. solids=86.3

Wt. Ave M.W.=2200

E.) Clearcoat Composition Grams

ResimineÒ 6550 14.43 (melamine from Monsanto) Nonaqueous Dispersion (A)26.77 Acrylosilane Resin (B) 11.6 Cyclosilane Oligomer (C) 22.22Silanated Star Polyester (D) 23.17 Catalyst Solution* 3.55 DibutylinDilaurate 0.2 Resiflow SÒ 0.4 (acrylic flow agent from Estron Chemical)Tinuvin 384 2.32 (UV Screener from CIBA Geigy) Tinuvin 123 2.2 (HinderedAmine light stabilizer from CIBA Geigy) *Catalyst solution CycatÒ 600(sulfonic acid from American Cyanamid) 48.0 AMP-95Ò (amine from AngusChemical) 10.8 methanol 41.2

This coating was applied over a black waterborne basecoat which hadalready received a warm air flash of 5 min at 82° C. The coating wascured for 30 min at 141° C. This coating exhibited good appearance,hardness, etch and mar resistance.

What is claimed is:
 1. A curable coating composition of a binder in anorganic solvent, the composition having a volatile organic content notexceeding 0.4 kilograms per liter, consisting essentially of: i) abinder selected from a linear or branched cycloaliphaticmoiety-containing oligomer or blend of said oligomers with a weightaverage molecular weight not exceeding 3,000, a polydispersity notexceeding 1.5 and functionality A or A plus B; and ii) an oligomericcrosslinker or blend of said crosslinkers with a weight averagemolecular weight not exceeding 3,000 and functionality C; components iand ii reacting at cure to form a three-dimensional network havingchains of substantially uniform, controllable molecular weight betweencrosslinks; wherein: said functionalities in components i and ii areselected from the group consisting of: A is hydroxyl and C isisocyanate; A is epoxy and C is isocyanate; A is hydroxyl and C ismelamine; A is aldimine or ketimine, B is optionally hydroxyl, and C isisocyanate; A is epoxy, B is hydroxyl and C is isocyanate; and A issilane, B is hydroxyl and C is melamine; the composition additionallycontaining up to 200 parts by weight, based on 100 parts of (i) and(ii), of pigment.